Elevator brake release monitoring

ABSTRACT

Brake release sensors for an elevator can be replaced by an arrangement wherein the brake release is determined from the force caused by the brake. This is achieved by providing measuring device for measuring the weight of an elevator car between the brake and the motor body so that the weight of the elevator car is measured only when the brake is on.

This application is a continuation of PCT International Application No.PCT/FI2016/050065, which has an International filing date of Feb. 2,2016, and which claims priority to European Patent Application No.15153686.9, filed Feb. 3, 2015, the entire contents of both of which areincorporated herein by reference.

FIELD OF THE INVENTION

The invention relates elevators and particularly to braking systems usedin elevators.

BACKGROUND OF THE INVENTION

Elevator systems are regulated all over the world. Regulations typicallyrelate to the security of an elevator. Each elevator must fulfill theregulations and these requirements are sometimes verified regularly.Typically elevators are inspected regularly and parts not filling therequirements must be changed. As elevators are typically used fortransporting passengers the security is an essential aspect. Thus, allaspects that can have a negative impact on the security should beeliminated. Sometimes a small failure in a part of the elevator may leadinto security issues.

One of the important issues is that the elevator is operating withoutadditional forces restricting the movement of the elevator car. Onepossible cause is a defected brake that is not completely released andcauses friction. The problem associated with this is the fact that thebrake wears very fast and will not have the required braking power whenit is needed. The wearing may be very fast and the dangerous technicalcondition occurs so that the conventional inspection frequency is notable to notice the wearing in time.

The problem mentioned above is regulated by many authorities and it isalso desirable without regulation to prevent the movement of theelevator car when the brake is not completely released so that possiblydangerous situation is avoided.

Conventionally displacement sensors have been used for detecting therelease of a brake. These sensors are additional components that are notalways reliable because the mechanical movement of a brake is verysmall. Furthermore, sometimes the brake does not open completely but thesensor indicates that the brake has been opened but it still has acontact which will cause friction and leads into undesired wearing asdiscussed above. A further drawback of additional sensor is that ingeneral, using additional components causes expenses because ofadditional components and additional design needed. Thus, there is aneed for reliable and cost efficient arrangement for brake releasemonitoring.

SUMMARY

The invention discloses an arrangement, wherein brake release sensorsfor an elevator can be replaced by an arrangement wherein the brakerelease is determined from the force caused by the brake. This isachieved by providing measuring device for measuring the weight of anelevator car between the brake and the motor body so that the weight ofthe elevator car is measured only when the brake is on.

An example of an elevator where a weight measuring device is arrangedbetween the brake and the motor body is disclosed in WO2013/182742 A1,wherein the measurement device is used for measuring the weight of anelevator car in order provide smooth start for an elevator and, forexample, detecting overweight situations. In the embodiment disclosed inthe publication mentioned above the weight of an elevator car ismeasured from a rotating shaft part of traction sheave when the break ison. This is a preferred way of measuring the weight as it will measurethe load actually caused to the traction sheave. Because of thisarrangement the measurement result should be zero when the brake isreleased the elevator is operated. However, if the brake is not openedcompletely and the brake drags, the weighing device will indicate avalue that deviates from the value of completely released brake.

An embodiment is implemented as a method for detecting release of abrake of an elevator. In the method a measuring device for measuringweigh of an elevator car from a rotating shaft of part a traction sheaveof the elevator when the brake of the elevator is closed is used. Then,when the brake is about to be released a brake release signal isgenerated. After the brake release signal values a value from themeasuring device generating the brake release signal are still received.Received values are compared with a reference value. A brake failure isdetected when the received value deviates from the reference value.

In an embodiment the method described above is implemented as a computerprogram embodied on a computer readable medium. The computer program isconfigured to cause the method described above when executed in acomputing device. In a further embodiment an apparatus is used to causethe method described above. In a further embodiment the above describedmethod, computer program or apparatus is implemented in an elevator.

The benefit of the invention is that it provides a reliable way ofreplacing conventional switches for detecting the brake release.Furthermore, as the arrangement suggested by the present invention ismore accurate it will fulfill the increased requirements by differentregulations around the world. A further benefit of the present inventionis that it provides cost savings compared to traditional switches byproviding reliable brake monitoring by weighing device of the elevator.Thus, no additional components are needed, which causes cost savings inmanufacturing and maintenance.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and constitute a part of thisspecification, illustrate embodiments of the invention and together withthe description help to explain the principles of the invention. In thedrawings:

FIG. 1 is a block diagram of an example embodiment of the presentinvention,

FIG. 2 is a flow chart of a method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings.

In FIG. 1 a block diagram of an arrangement according to the presentinvention. In the embodiment of FIG. 1 an elevator car 10 is operated byusing a hoisting rope 11 which is arranged to a traction sheave 12,which is operated by the hoisting machine 13. The elevator car 10transports passengers according to given calls. The hoisting machine ofthe embodiment is controlled by a controller 16 that is connected to thehoisting machine 13. For example, when the controller receives a call,directly or indirectly, from the elevator car, it will instruct thehoisting machine to move the elevator to the called floor. When theelevator is not moving it will be kept in its position by a break 14.The break is typically magnetic so that an electromagnetic force is usedto keep the brake released during the movement of the elevator car. Whenthe elevator car stops the brake closes when the electromagnetic forceis turned off. In the embodiment of figure a weighing device 15 isarranged between the brake 14 and traction sheave 12 so that theweighing device 15 is able to measure the weight of the elevator carwhen the brake 14 is in closed position. The present invention is notlimited to any brake or hoisting machine type but any hoisting machineand brake type can be used, provided that they can be configured in amanner that the weight of the elevator car is measured only when thebrake is in closed position. Examples of suitable brake, measuringdevice and hoisting machine are given, for example, in WO2013/182742 A1mentioned above.

In the embodiment according to FIG. 1 hoisting machine 13, weighingdevice 15 and brake 14 are connected to the controller 16. In the figurea separate connection between each of the components is disclosed,however, it is possible that the arrangement comprises a furthercontroller at the vicinity of the hoisting machine or hoistingarrangement and the information is then transmitted further to thecontroller. Conventionally the weighing device 15 has been used forproviding a smooth start for elevator ride by estimating the forceneeded from the weight of the elevator car. A further use has been todetect possible overload situations when the elevator car is too heavy.When the elevator is overloaded the operation of the elevator should beprevented for security reasons. In other words, conventionally theweighing device has been used between the rides when the elevator car isstationary in a floor waiting for a next call or having a stop in afloor when the elevator rides have been called to a plurality ofdestinations.

When the arrangement of FIG. 1 is operated the controller 16 receivescalls and schedules the movement of the elevator car 10. During theoperation it may receive indications from and can send instructions tothe elevator car 10, hoisting machine 13, brake 14 and weighing device15. According to the embodiment of FIG. 1 the release of the brake 14can be detected using, for example, a method discussed below with regardFIG. 2. In the method the controller 16 detects or receives anindication that the brake release signal has been generated and/or theelevator is moving. At the same time it will continue receiving datafrom weighing device 15. When the brake 14 and weighing device 15 areconfigured as discussed above, there should not be any load to bemeasured if the brake 14 is released completely. If the weighing device,however, indicates a value different to the value without load it mightbe an indication of a brake failure. The different value is caused bydragging brake.

The controller 16 further includes at least one processor 17 and atleast one memory 18 for storing and executing computer programs andrelated data. Furthermore, the controller 16 may include othercomponents that are not shown in the figure, for example, datacommunications connection if the controller is located at a remote siteso that the data can be received and instructions transmitted throughthis data communication connection.

In FIG. 2 a method according to the present invention is disclosed. Themethod is initiated by generating brake release signal, step 20. Forexample, if the controller 16 of FIG. 1 is responsible for monitoringand instructing the operation of the elevator system, the brake releasesignal may be an internal message within the software frameworkoperating the elevator. Thus, when the software component responsiblefor instructing brake release sends an instruction for brake release itsimultaneously sends message to monitoring component that the brake hasbeen released. As a response to the brake release signal the brake isreleased, or if the brake is defect, at least tried to release.

The monitoring component receives values from the weight measuringdevice, step 21. When the brake is in closed position the monitoringmeans receive the weight of the elevator car. When the brake is releasedthe value received should be zero if the weighing device is calibratedto show zero when there is no load. The received value is compared to areference value, step 22. It is important to understand that theweighing device does not necessarily show zero when there is no load butmay deviate from zero. This offset value may be determined by monitoringthe values that the weighing device provides and if it is the same valueto both elevator operating directions the value can be considered as anoffset from zero and used as a reference value. If the measured valuedeviates from this reference value, there may be a brake problem and itis detected, step 24. Correspondingly, if the reference value cannot bedetermined, i.e., the weighing device shows different values todifferent directions, there may be a brake problem.

After detecting the brake problem different actions may be taken. Forexample, the elevator may be brought to the next floor and stoppedthere. The operation of that elevator may be prevented and a maintenancecall may be launched.

The above mentioned method may be implemented as computer software whichis executed in a computing device, such as the controller 16 of FIG. 1.When the software is executed in a computing device it is configured toperform the above described inventive method. The software is embodiedon a computer readable medium so that it can be provided to thecomputing device, such as the controller 16 of FIG. 1.

As stated above, the components of the exemplary embodiments can includecomputer readable medium or memories for holding instructions programmedaccording to the teachings of the present inventions and for holdingdata structures, tables, records, and/or other data described herein.Computer readable medium can include any suitable medium thatparticipates in providing instructions to a processor for execution.Common forms of computer-readable media can include, for example, afloppy disk, a flexible disk, hard disk, magnetic tape, any othersuitable magnetic medium, a CD-ROM, CD±R, CD±RW, DVD, DVD-RAM, DVD±RW,DVD±R, HD DVD, HD DVD-R, HD DVD-RW, HD DVD-RAM, Blu-ray Disc, any othersuitable optical medium, a RAM, a PROM, an EPROM, a FLASH-EPROM, anyother suitable memory chip or cartridge, or any other suitable mediumfrom which a computer can read.

It is obvious to a person skilled in the art that with the advancementof technology, the basic idea of the invention may be implemented invarious ways. The invention and its embodiments are thus not limited tothe examples described above; instead they may vary within the scope ofthe claims.

1. A method for detecting release of a brake of an elevator, whichmethod comprises: using a measuring device for measuring weight of anelevator car from a rotating shaft of part a traction sheave of saidelevator when the brake of said elevator is closed; generating a brakerelease signal; receiving a value from said measuring device; comparingsaid received value to a reference value; and detecting a brake failurewhen said received value deviates from said reference value.
 2. Themethod according to claim 1, the method further comprises transmittingan error message as a response to said detected failure.
 3. The methodaccording to claim 1, the method further comprises moving said elevatorto the next floor responsive to detecting the brake failure.
 4. Themethod according to claim 1, wherein the method further comprisespreventing use of said elevator after detecting a brake failure.
 5. Themethod according to claim 1, wherein said reference value is the valuethat corresponds with the situation wherein said measuring device isunloaded.
 6. The method according to claim 5, wherein said value iszero.
 7. The method according to claim 1, wherein determining saidreference value by driving the elevator to both directions and acceptingthe value indicated by the measurement device as a reference value whenthe measurement device indicates same value to both directions.
 8. Acomputer program for a computing device comprising code adapted to causethe method according to claim 1 when executed on a data-processingsystem.
 9. An apparatus comprising: processor; at least one memory;wherein the apparatus is configured to perform the method according toclaim
 1. 10. An elevator system comprising at least one elevatorcomprising the apparatus according to claim 9.